They were throwing rocks from the north bridge abutment above an active railroad track, the release said.

Police did not locate any suspects during an initial search about 12:10 p.m., but received more calls two hours later regarding rock throwing in the same area, the release said.

This time, officers found numerous rocks and railroad spikes on the interstate, the release said. Police got a description of the rock-throwers and found two teenagers who matched the descriptions at a nearby town-home complex, the release said